The invention relates to cooling systems for dynamoelectric machines and more particularly, to the cooling of exciter assemblies having rotating rectifier diodes.
In dynamoelectric machines, particularly synchronous generators having exciter assemblies which include rotating exciter windings along with rectifier diodes for converting the AC current generated in the exciter windings into a DC field current, effective cooling of the exciter assembly is of great importance. This is especially true for certain classes of synchronous generators such as high speed aircraft generators, where the operating environment is restricted and weight requirements are critical.
One particularly effective approach to cooling the exciter assembly and rectifier diodes is to have a coolant, such as oil, sprayed directly on the rectifier diodes. In one type of synchronous generator the diodes are supported by plates which are in turn secured to a hub which rotates with the generator shaft. The hub also serves to support the rotating exciter windings. However, since the cooling oil generally contains minute particles of metal and other substances, the centrifugal force resulting from the rotation of the hub will tend to cause accumulations of the metals and the other substances to build up on the inner surface of the hub. Practical experience has shown that the sludge build-ups can become large enough that they will short the plates to the hub, causing a short circuit and thus, the failure of the generator. As a result, it has become extremely important, from a practical standpoint, to provide means for eliminating this type of sludge build-up while maintaining efficient cooling.